I1, modulates the more rapidly varying second factor that depends upon the number of slits and their spacing. Estimation An envelope detector is an electronic circuit that extracts the envelope from a signal. In digital signal processing, the envelope may be estimated employing the Hilbert transform or a moving RMS amplitude. See also Empirical mode decomposition Envelope (mathematics) Envelope tracking Instantaneous phase Modulation Mathematics of oscillation Peak envelope power Spectral envelope References Interference Interferometry Waves Radio modulation modes Radio electronics